Windows rolled down at high speed (effect on fuel consumption?)

[daniel_hc]

One of the 100+ hypermiling tips is about having window up to avoid aerodynamic drag at high speed. Does anyone have an idea how much this affect the fuel-consumption?

What is your experience?

[jtbo]

Originally Posted by daniel_hc

One of the 100+ hypermiling tips is about having window up to avoid aerodynamic drag at high speed. Does anyone have an idea how much this affect the fuel-consumption?

What is your experience?

In other that city cruising speeds it was more than effect of AC from my memory.

[tru]

in my truck...it doesnt matter.

in my car, anything above 45 and its about tied with the A/c

[mcrews]

i rsn this test on my infiniti Q45 (2002) and my Jaguar Vanden Plas (1999). both lost 3-4mpg with the windows down as compared to windows up w/ ac.
I recently put window visors on the Q45 and run with the windows down about 1" on comfortable days.
There is barely a 1mpg differance than w/ ac on.

[NeilBlanchard]

I have found that cracking the front windows open about 1/2" can actually help the drag, and a lot more air comes in the dash vents. This gives much better FE than using the A/C or opening the windows more.

[larrybuck]

I try NEVER to go w windows more than 2" down.

In the search area (upper left of page) check out: The Deadly Heat, and: Hot Weather: Dirt cheap cooling help

[daniel_hc]

Thanks guys for all the answers

[Nerys]

same here. instant readings drop about 4mpg with windows wide open.

no visible change with windows just open slightly (inch or so)

I have a new guino that should be "less jumpy" so I might get better "real time" data :-)